Workpiece supply/conveyance device and machine tool with the workpiece supply/conveyance device

ABSTRACT

There is provided a workpiece supply/conveyance device that can remove a workpiece from a spindle and supply another workpiece to the spindle smoothly and in a short time. A workpiece holding section of one of a plurality of arms includes an unmachined workpiece holding section  29  for holding an unmachined workpiece and a machined workpiece holding section  21  for holding a machined workpiece. When the plurality of arms are rotated in one direction, each of the arms is moved to an unmachined workpiece loading position III at which the unmachined workpiece holding section receives the unmachined workpiece, a standby position IV in a standby state while holding the unmachined workpiece to be next machined in the unmachined workpiece holding section, a workpiece delivery/reception position I at which the workpiece is delivered and received among a workpiece machining apparatus, the unmachined workpiece holding section and the machined workpiece holding section, and a machined workpiece unloading position II at which the machined workpiece held in the machined workpiece holding section is unloaded.

TECHNICAL FIELD

The present invention relates to a workpiece supply/conveyance devicewhich delivers and receives a workpiece to and from a workpiecemachining apparatus such as a machine tool, and a machine tool includingthis workpiece supply/conveyance device.

BACKGROUND ART

A machine tool is known which machines a workpiece attached to a spindleby using a tool disposed on a tool rest which can relatively move withrespect to the spindle or a table. Among such machine tools, there isknown a machine tool including a workpiece supply/conveyance devicewhich automatically convey a machined workpiece from the spindle andautomatically supplies an unmachined workpiece to the spindle.

A workpiece supply/conveyance device of a machine tool disclosed inPatent Document 1 includes a plurality of arms radially expanding from acommon rotation center. Each arm is integrally rotated around therotation center as a supporting point, and a position of each arm issequentially switched to a machined workpiece conveying position, aworkpiece supply position, a standby position, and a workpiecedelivery/reception position facing the spindle, whereby an unmachinedworkpiece is prepared and delivered to the spindle, and a machinedworkpiece is received from the spindle and then conveyed.

Further, a loading device disclosed in Patent Document 2 includes fourarms which rotate in forward and reverse directions simultaneouslyperforms an operation of delivering an unmachined workpiece from an armA to one of two spindles arranged in parallel when the four arms areplaced at predetermined positions, an operation of delivering ahalf-machined workpiece to the other spindle from an arm B, and anoperation of delivering the half-machined workpiece to an arm C, andthen simultaneously carries out the loading of the unmachined workpieceto the arm A and the unloading of a machined workpiece from an arm D,when the four arms are integrally rotated to be placed at nextpredetermined positions.

However, in the workpiece supply/conveyance device disclosed in each ofDocuments 1 and 2, the workpiece loading arm which delivers theunmachined workpiece to the spindle and the workpiece unloading armwhich receives the machined workpiece from the spindle are separatelydisposed. Therefore, after the workpiece unloading arm has received themachined workpiece from the spindle, until the workpiece loading armwhich holds an unmachined workpiece rotates to a position where it facesthe spindle, a long time is required, and hence there is a problem thata cycle time is prolonged.

Patent Document 1: Japanese Patent Application Laid-open No. 155196-1983Patent Document 2: Japanese Patent Application Laid-open No. 75901-1986DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

The present invention has been developed in view of the above-describedproblem. An object of the present invention is to provide a workpiecesupply/conveyance device which can load and unload a workpiece in asimple constitution and can further curtail a cycle time, and anotherobject thereof is to provide a machine tool including this workpiecesupply/conveyance device.

Means for Solving the Problem

To achieve the above objects, there is provided a workpiecesupply/conveyance device which includes a plurality of arms radiallyextending from a rotation center, integrally rotates the plurality ofarms around a rotation center, and places a workpiece holding section ofone arm in the plurality of arms at a workpiece delivery/receptionposition to deliver/receive the workpiece between a workpiece machiningapparatus and the workpiece holding section, wherein the workpieceholding section includes an unmachined workpiece holding section thatholds an unmachined workpiece and a machined workpiece holding sectionthat holds a machined workpiece, and the plurality of the arms areintegrally rotated in one direction to move each of the arms to anunmachined workpiece loading position at which the unmachined workpieceis received by the unmachined workpiece holding section, a standbyposition which is in a standby mode while holding the unmachinedworkpiece to be next machined in the unmachined workpiece holdingsection, a workpiece delivery/reception position at which the workpieceis delivered and received among the workpiece machining apparatus, theunmachined workpiece holding section and the machined workpiece holdingsection, and a machined workpiece unloading position at which themachined workpiece held in the machined workpiece holding section isunloaded.

In this case, the unmachined workpiece holding section and the machinedworkpiece holding section of the workpiece holding section are arrangedin close proximity to each other on a common circumference having therotation center as the center, and the arm is rotated in one directionwhen placed at the workpiece delivery/reception position, whereby thearm may be moved between a machined workpiece reception position atwhich the machined workpiece holding section receives the machinedworkpiece from the workpiece machining apparatus and an unmachinedworkpiece delivery position at which the unmachined workpiece holdingsection delivers the unmachined workpiece to the workpiece machiningapparatus.

Further, when one of the plurality of arms is at the standby position,one of the plurality of other arms is at the unmachined workpieceloading position, and the workpiece supply/conveyance device may beprovided with a loading device which supplies the unmachined workpieceto the arm placed at the unmachined workpiece loading position.

Furthermore, when one of the plurality of arms is at the standbyposition, one of the plurality of other arms is at the machinedworkpiece unloading position, and the workpiece supply/conveyance devicemay be provided with an unloading device which receives the machinedworkpiece from the arm placed at the machined workpiece unloadingposition and unloads the same.

The plurality of loading devices may be provided in a path along whichthe arm moves from the machined workpiece unloading position to thestandby position.

In the present invention, a position of the arm may be shifted in theorder of the unmachined workpiece loading position, the standbyposition, the workpiece delivery/reception position, and the machinedworkpiece unloading position.

A machine tool of the present invention comprises a spindle which holdsa workpiece; a tool rest having a tool to machines the workpiece held bythe spindle; and a workpiece supply/conveyance device which delivers andreceives the workpiece to and from the spindle. The workpiecesupply/conveyance device comprises a plurality of arms radiallyextending from a rotation center, and an unmachined workpiece holdingportion to hold an unmachined workpiece and a machined workpiece holdingsection to hold a machined workpiece which are provided to each of thearms, and the plurality of the arms are integrally rotated in onedirection to move each of the arms to an unmachined workpiece loadingposition at which the unmachined workpiece is received by the unmachinedworkpiece holding section, a standby position which is in a standby modewhile holding the unmachined workpiece to be next machined in theunmachined workpiece holding section, a workpiece delivery/receptionposition at which the workpiece is delivered and received among theworkpiece machining apparatus, the unmachined workpiece holding sectionand the machined workpiece holding section, and a machined workpieceunloading position at which the machined workpiece held in the machinedworkpiece holding section is unloaded.

In this case, the unmachined workpiece holding section and the machinedworkpiece holding section of the workpiece holding section are arrangedin close proximity to each other on a common circumference having therotation center as the center, and the arm is rotated in one directionwhen placed at the work delivery/reception position, whereby the arm maybe moved between a machined workpiece reception position at which themachined workpiece holding section receives the machined workpiece fromthe workpiece machining apparatus and an unmachined workpiece deliveryposition at which the unmachined workpiece holding section delivers theunmachined workpiece to the workpiece machining apparatus.

Further, when one of the plurality of arms is at the standby position,the workpiece grasped by the spindle is preferably machined.

Furthermore, when one of the plurality of arms is at the standbyposition, one of the plurality of other arms is at the unmachinedworkpiece loading position, and the machine tool may be provided with aloading device which supplies the unmachined workpiece to the arm placedat the unmachined workpiece loading position.

In addition, when one of the plurality of arms is at the standbyposition, one of the plurality of other arms is at a machined workpieceunloading position, and the machine tool may be provided with anunloading device which receives the machined workpiece from the armplaced at the machined workpiece unloading position and unloads thesame.

Further, the plurality of loading devices may be provided in a pathalong which the arm moves from the machined workpiece unloading positionto the standby position.

In this case, while different types of workpieces supplied from theplurality of loading devices are exchanged, the workpieces may bemachined. Furthermore, in the present invention, a position of the armis preferably shifted in the order of the unmachined workpiece loadingposition, the standby position, the workpiece delivery/receptionposition, and the machined workpiece unloading position.

As another embodiment of the machine tool according to the presentinvention, a tool is attached to the arm, and the workpiece may bemachined by the tool with the aid of an swing operation of the arm.

Effect of the Invention

According to the thus constituted present invention, when thedelivery/reception of the machined workpiece and the unmachinedworkpiece with respect to the spindle ends and the arm moves away fromthe spindle, the arm which holds an unmachined workpiece which is to benext machined can be set in a standby mode at a standby position nearthe spindle. Therefore, after the end of the machining of the workpieceon the spindle, the arm can be immediately rotated from the standbyposition to be placed at the workpiece delivery/reception position whereit faces the spindle.

Furthermore, since the unmachined workpiece holding section and themachined workpiece holding section can be disposed on one arm in closeproximity to each other, a relative distance between the spindle or thelike and the arm can be minimized in a process of the reception of themachined workpiece from the spindle or the like to the delivery of theunmachined workpiece to the spindle or the like, which enables thecurtailment of the cycle time.

In particular, the unmachined workpiece holding section and the machinedworkpiece holding section are disposed on one circumference (A), andhence the delivery/reception of the machined workpiece and theunmachined workpiece between the spindle or the like and the arm ispossible by the slight rotating operation only of the arm.

As explained above, the present invention can perform the unloading andthe loading of the workpiece in a short time by a simple operation whichis the rotation of the arm in one direction, and hence it has an effectthat a time from the machining end to the machining start of a workpiece(a cycle time) in a workpiece machining apparatus such as a machine toolcan be curtailed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 show an embodiment of a machine tool including a workpiecesupply/conveyance device according to the present invention, where (a)is a front view in which a tool rest is omitted and (b) is an enlargedview of an arm tip portion;

FIG. 2 is a plan view of the machine tool in FIG. 1;

FIG. 3 is an enlarged cross-sectional view showing the tip portion ofthe arm on which an unmachined workpiece holding section and a machinedworkpiece holding section are provided;

FIG. 4 is a view for explaining an operation of the reception of theunmachined workpiece from a loading device to the delivery of themachined workpiece to an unloading device;

FIG. 5 is a view for explaining the operation of the reception of theunmachined workpiece from the loading device to the delivery of themachined workpiece to the unloading device;

FIG. 6 is an enlarged front view of a main part for explaining abehavior of the rotation of the arm when delivering/receiving theworkpiece between a spindle and the arm;

FIGS. 7( a) and 7(b) show a second embodiment of the present invention,where (a) is a front view of a main part of a machine tool including aworkpiece supply/conveyance device and (b) is a plan view of the same;

FIGS. 8( a) and 8(b) each is an enlarged cross-sectional view of the tipportion of a spindle in the machine tool according to the secondembodiment of the present invention;

FIG. 9 shows a modification of the second embodiment according to athird embodiment of the present invention;

FIG. 10 shows another modification of the second embodiment according toa fourth embodiment of the present invention;

FIG. 11 is a front view for explaining a constitution of an arm bodyaccording to a fifth embodiment of the present invention;

FIG. 12 is a front view for explaining a constitution of an arm bodyaccording to a sixth embodiment of the present invention; and

FIG. 13 is an enlarged view of the tip portion of an arm having a toolattached thereto.

DESCRIPTION OF REFERENCE NUMERALS

1: machine tool

10: spindle stock

13: spindle

2: workpiece supply/conveyance device

21: machined workpiece holding section

24, 240, 340: arm

26, 260, 360: arm body

27: loading device

28: unloading device

29: unmachined workpiece holding section

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of a workpiece supply/conveyancedevice and a machine tool including this workpiece supply/conveyancedevice according to the present invention will be described withreference to the accompanying drawings.

It is to be noted that the description will be given about a case wherethe workpiece supply/conveyance device according to the presentinvention is applied to a machine tool as an example of a workpiecemachining apparatus in this embodiment.

FIRST EMBODIMENT

FIG. 1 show an embodiment of a machine tool including a workpiecesupply/conveyance device of the present invention, where (a) is a frontview in which a tool rest is omitted and (b) is an enlarged view of anarm tip portion, and FIG. 2 is a plan view of the machine tool in FIG.1.

[Constitution of Machine Tool]

As shown in FIG. 1( a) and FIG. 2, a machine tool 1 is provided on apedestal 11, and it has a spindle stock 10 which can freely move forwardand backward along a Z direction (a direction orthogonal to a pagesurface of FIG. 1), a spindle 13 which is rotatably supported on thisspindle stock 10 and includes a chuck (not shown) that grasps aworkpiece at a front end, and a comb-blade-like tool rest 12 which isarranged in front of the spindle 13 to face the same and has a pluralityof tools T attached thereto. The workpiece grasped by the chuck ismachined by the relative movement of the tool rest 12 and the spindle13.

It is to be noted that the “relative movement” in this specification isa concept including a case where the spindle 13 moves with respect tothe tool rest 12, a case where the tool rest 12 moves with respect tothe spindle 13, and a case where both the spindle 13 and the tool rest12 move.

[Constitution of Workpiece Supply/conveyance Device]

The workpiece supply/conveyance device 2 is provided at a position whereit does not interfere with the spindle 3, the tool rest 12, and thetools T. The workpiece supply/conveyance device 2 delivers an unmachinedworkpiece to the chuck at the front end of the spindle 3, receives amachined workpiece from the chuck, and unloads it from the machine tool1.

The workpiece supply/conveyance device 2 includes an arm body 26 havinga plurality of arms 24 radially projecting from a rotation center C1.The arm body 26 is arranged between the spindle 13 and the tool rest 12.Further, the arm body 26 is rotatably supported by a support section 20fixed to the pedestal 11 above the spindle stock 10.

On the support section 20, a rotary shaft 20 a which is rotated by adriving means not shown is arranged on an axial line of the rotationcenter C1 of the arms 24. The arm body 26 is disposed to the tip of thisrotary shaft 20 a.

The four arms 24 in the arm body 26 are provided at intervals of 90degrees.

As shown in the enlarged view of FIG. 1( b), at the tip of each arm 24,an unmachined workpiece holding section 29 which delivers an unmachinedworkpiece to the spindle 13 and a machined workpiece holding section 21which receives a machined workpiece from the spindle 13 are provided tobe adjacent to each other.

All the unmachined workpiece holding sections 29 and all the machinedworkpiece holding sections 21 of all the arms 24, 24 . . . are arrangedon a common circumference A having the rotation center C1 as the center.In this embodiment, the arm body 26 rotates in a counterclockwisedirection (a direction indicated by an arrow in each of FIGS. 1( a) and(b)) as the machine tool 1 is seen from the front side, each machinedworkpiece holding section 21 is arranged on a downstream side of therotating direction as seen from the spindle 13. On an upstream side ofthe same, each unmachined workpiece holding section 29 is arranged.

When one of the machined workpiece holding section 21 and the unmachinedworkpiece holding section 29 (e.g., the machined workpiece holdingsection 21) delivers and receives the workpiece to and from the chuck ofthe spindle 13, the machined workpiece holding section 21 and theunmachined workpiece holding section 29 are preferably provided asclosely to each other as possible, so long as the workpiece held by theother thereof (e.g., the unmachined workpiece holding section 29) doesnot interfere with the spindle 13.

The arm body 26 is arranged in such a manner that an axial line C2 ofthe spindle 13 is placed on the circumference A. The arm body 26 isrotated around the rotation center C1 as an axial center by the drivingmeans. The driving means can precisely rotate the arm body 26 as much asa preset rotation angle to position the same. As this type of drivingmeans, a known driving means such as a servo motor, a stepping motor, ora motor having an encoder can be used.

The unmachined workpiece holding section 29 is formed in accordance witha shape or a dimension of the unmachined workpiece to enable holding theunmachined workpiece, and the machined workpiece holding section 21 isformed in accordance with a shape or a dimension of the machinedworkpiece to enable holding the machined workpiece.

FIG. 3 is an enlarged cross-sectional view of the tip portion of the arm24. In this embodiment, an unmachined workpiece WB and a machinedworkpiece WA can be held by the machined workpiece holding section 21and the machined workpiece holding section 29 having the sameconstitution. Therefore, the same reference numeral denotes theunmachined workpiece holding section 29 and the machined workpieceholding section 21, as both the sections are shown in FIG. 3.Furthermore, when it is necessary to discriminate the unmachinedworkpiece and the machined workpiece from each other in the followingdescription, the unmachined workpiece is denoted by reference character“WB” and the machined workpiece is done by reference character “WA”.

Each of the unmachined workpiece holding section 29 and the machinedworkpiece holding section 21 is fitted into a through hole 24 a formedat the tip of the arm 24. Each section includes a cylindrical holder 291having about the same internal diameter as an external diameter of eachof the unmachined workpiece WB and the machined workpiece WA, and astopper 292 which is fitted into this holder 291 from one side thereofand comes into contact with the unmachined workpiece WB or the machinedworkpiece WA to position the unmachined workpiece WB or the machinedworkpiece WA in the holder 291. Moreover, the stopper 292 is providedwith a hole 292 a into which a shaft portion WAa formed at the tip ofthe machined workpiece WA is inserted. In addition, the holder 291 maybe provided with urging means constituted of such a ball 291 a and aspring 291 b as shown in the drawing so that each of the unmachinedworkpiece WB and the machined workpiece WA is not readily dropped off.

Thus, the machined workpiece WA can be delivered to the machinedworkpiece holding section 21, for example, by positioning the machinedworkpiece holding section 21 and the spindle 13 so as to be opposite toeach other on one axial line, and then advancing the spindle 13 towardthe arm 24 along the axial line to push the machined workpiece WA heldby the chuck of the spindle 13 into the holder 291 of the machinedworkpiece holding section 21. Additionally, in a case where the machinedworkpiece WA cannot be sufficiently pushed into the holder 291 only bythe advancing movement of the spindle 13, for example, a push rod whichcan pass through a through hole of the spindle 13 and can freely moveforward and backward may be provided, and this push rod may be utilizedto push the machined workpiece WA into the machined workpiece holdingsection 21.

Furthermore, the unmachined workpiece WB can be delivered from theunmachined workpiece holding section 29 to the spindle 13, for example,by positioning the unmachined workpiece holding section 29 and thespindle 13 so as to be opposite to each other on one axial line,advancing the spindle 13 having the opened chuck toward the arm 24 alongthe axial line, and inserting, into the chuck, the tip of the unmachinedworkpiece WB held by the unmachined workpiece holding section 29 in astate where a part of the tip projections, and then closing the chuck.Also in this case, when a length of the projected tip is not sufficient,for example, a push rod which can pass through the through hole of theholder 291 may be utilized to push out the unmachined workpiece WBtoward the spindle 13.

The workpiece supply/conveyance device of the present invention mayinclude one or both of a loading device which supplies the unmachinedworkpiece to the arm and an unloading device which receives the machinedworkpiece from the arm and unloads the same. When such a loading deviceor an unloading device is provided, continuous unmanned machining ispossible for a long time.

In this embodiment, the workpiece supply/conveyance device 2 includes aloading device 27 which supplies, to the arm 24, the unmachinedworkpiece WB which is delivered to the spindle 13 and an unloadingdevice 28 which conveys the machined workpiece WA delivered from thespindle 13 to the arm 24 to the outside of the machine tool 1.

As each of the loading device 27 which loads the unmachined workpieceand the unloading device 28 which unloads the machined workpiece, aknown device such as a belt conveyer, a loader device, a robot hand, ora part feeder can be used.

When the driving means is driven, the arm body 26 can sequentiallyposition each arm 24 to predetermined rotation angle positions, i.e., aworkpiece delivery/reception position (indicated by reference numeral Iin FIG. 1) at which the machined workpiece holding section 21 or theunmachined workpiece holding section 29 of the arm 24 faces the spindle13, a machined workpiece unloading position (indicated by referencenumeral II) at which the machined workpiece is delivered to theunloading device 28 from the machined workpiece holding section 21, anunmachined workpiece loading position (indicated by reference numeralIII) at which the unmachined workpiece is supplied to the unmachinedworkpiece holding section 29 from the loading device 27, and a standbyposition (indicated by reference numeral IV) which is a position that isas close to the spindle 3 as possible on the upstream side in therotating direction as seen from the spindle 13 and at which the spindle13, the tool rest 12 and the tools T during the machining of theworkpiece do not interfere with each other.

In this embodiment, when one arm 24 is placed at the standby positionIV, two arms 24 in the three remaining arms are simultaneously placed atthe machined workpiece unloading position II and the unmachinedworkpiece loading position III, and the other arm 24 is placed on theopposite side (indicated by reference numeral V in FIG. 1) of the arm 24at the standby position IV over the spindle 13 as seen from the frontside. The loading device 27 is arranged to face the unmachined workpieceholding section 29 of the arm 24 placed at the unmachined workpieceloading position III, and the unloading device 28 is arranged to facethe machined workpiece holding section 21 of the arm 24 placed at themachined workpiece unloading position II.

Therefore, while the one arm 24 is standby at the standby position IV,the unmachined workpiece can be supplied to the other arm 24, and at thesame time, the machined workpiece can be unloaded from the further otherarm 24. Hence, no wasting time is present.

The machine tool 1 of this embodiment cuts, with the tools T, theworkpiece held by the chuck of the spindle 13 while one arm 24 isstandby at the standby position IV. At the standby position IV, sinceeach arm 24 does not interfere with the spindle 13, the tool rest 12 andthe tools T during the machining of the workpiece, the workpiece can bemachined freely including the forward and backward movement of thespindle 13.

Next, a function of the workpiece supply/conveyance device 2 having theabove-described constitution will be described with reference to FIGS. 4to 6.

FIGS. 4 and 5 are views for explaining an operation of the reception ofthe unmachined workpiece from the loading device 27 to the delivery ofthe machined workpiece to the unloading device 28, and FIG. 6( a) andFIG. 6( b) are enlarged front views of a main part for explaining thebehavior of the rotation of the arm 24 when delivering/receiving theworkpiece between the spindle 13 and the arm 24.

In the following description, a state that one arm 24 is placed at thestandby position IV as shown in FIG. 1( a) will be explained as an“initial state”.

In this initial state, the workpiece is machined at the spindle 13. Atthe unmachined workpiece loading position III, the unmachined workpieceWB is supplied from the loading device 27 to the unmachined workpieceholding section 29 of the arm 24, and at the machined workpieceunloading position II, the machined workpiece WA is delivered from themachined workpiece holding section 21 to the unloading device 28, andthen unloaded.

FIG. 4( a) shows a behavior that the unmachined workpiece WB is suppliedfrom the loading device 27 to the unmachined workpiece holding section29 of the arm 24. As shown in the drawing, the unmachined workpiece WBis pushed into the holder 291 of the unmachined workpiece holdingsection 29 by, e.g., a push rod 275 provided in the loading device 27until the workpiece comes into contact with the stopper 292. It is to benoted that, for example, air pressure can be also utilized for thepushing, in addition to a push rod 133.

Since the unmachined workpiece WB is supplied to a workpiece supplysection 29 when the arm 24 is placed at the unmachined workpiece loadingposition III, the arm 24 placed at the standby position IV holds theunmachined workpiece WB which is to be next machined during the standbyat the standby position IV.

When machining the workpiece held by the chuck of the spindle 13 isterminated, the spindle 13 moves back to a position where the movementof the arm 24 is not obstructed. Then, the arm body 26 rotates to movethe arm 24 placed at the standby position IV to the workpiecedelivery/reception position I where it faces the spindle 13. The armbody 26 first places, on the axial line C2 of the spindle 13, themachined workpiece holding section 21 of the arm 24 placed at theworkpiece delivery/reception position I, as shown in FIG. 4( a) and FIG.6( a). A position of the arm 24 at this time is a workpiece receptionposition Ia.

Thereafter, the spindle 13 moves forward and uses the push rod 133 asrequired as described above to insert the tip of the machined workpieceWA into the holder 291 of the machined workpiece holding section 21.

In this embodiment, the push rod 133 is inserted and provided in athrough hole of a draw bar 132 which moves forward and backward thechuck 131 of the spindle 13. This push rod 133 can move forward andbackward along a direction of the axial line C2 of the spindle 13 bydriving means such as a cylinder. In a state where the chuck 131 isopened, the push rod 133 can push the machined workpiece WA into theholder 291 until this workpiece reaches the stopper 292 as shown in FIG.4( c). It is to be noted that the shaft portion WAa at the tip of themachined workpiece WA is placed in the hole 292 a of the stopper 292.

When the machined workpiece WA is delivered to the holder 291 of themachined workpiece holding section 21, the spindle 13 moves back to aposition where it does not interfere with the arm 24 in a state wherethe chuck 131 is opened. Thereafter, the arm body 26 rotates to place,on the axial line C2 of the spindle 13, the unmachined workpiece holdingsection 29 of the arm 24 placed at the workpiece delivery/receptionposition I, as shown in FIGS. 5( a) and 6(b). A position of the arm 24at this time is a workpiece delivery position Ib. Then, as depicted inFIG. 5( b), the spindle 13 moves forward to place, in the opened chuck131, the tip of the unmachined workpiece WB held by the unmachinedworkpiece holding section 29.

Afterward, when the chuck 131 is closed to hold the unmachined workpieceWB at the front end of the spindle 13, the spindle 13 moves back to theposition where it does not interfere with the rotation of the arm 24.

In the workpiece supply/conveyance device 2 of the present invention,the machined workpiece holding section 21 and the unmachined workpieceholding section 29 are provided to the one arm 24 as closely to eachother as possible so as to be adjacent to each other on the commoncircumference A, and hence the arm 24 placed at the workpiecedelivery/reception position I can be moved from the workpiece receptionposition Ia to the workpiece delivery position Ib, by rotating the armbody 26 as much as a very small angle range, whereby a delivering stateof the machined workpiece from the spindle 13 to the arm 24 can beswitched to a delivering state of the unmachined workpiece from the arm24 to the spindle 13. Therefore, there is an advantage that thereception of the workpiece from the spindle 13 and the delivery of theworkpiece to the spindle 13 can be carried out in a short time.

When the delivery and the reception of the machined workpiece WA and theunmachined workpiece WB with respect to the spindle 13 are terminated,the arm body 26 rotates to place, at the standby position IV, the arm 24placed at the workpiece supply position III in a state where theunmachined workpiece WB which is to be next machined is held. At thistime, the arm 24 which has received the machined workpiece WA from thespindle 13 at the workpiece delivery/reception position I immediatelybefore the rotation of the arm body 26 is placed at the position V, andthe arm 24 which has been placed at the position V immediately beforethe rotation of the arm 26 and holds the machined workpiece WA is placedat the machined workpiece unloading position II.

The machining of the unmachined workpiece WA delivered from the arm 24to the spindle 13 is started by the tools T on the tool rest 12 beforeand after the arm 24 holding the unmachined workpiece WB which is to benext machined reaches the standby position IV (see FIG. 5( c)).

At the machined workpiece unloading position II, the machined workpieceholding section 21 of the arm 24 holding the machined workpiece WA facesthe unloading device 28, and hence, as shown in FIG. 5( d), the machinedworkpiece WA can be pushed out from the holder 291 and delivered to theunloading device 28 by, e.g., inserting the push rod 285 provided in theunloading device 28 into the holder 291.

As explained above, each arm 24 of the arm body 26 is sequentiallyswitched to the workpiece delivery/reception position I, the workpieceejection position II, the workpiece supply position III and the standbyposition IV to carry out the above-mentioned respective operations atthe respective positions.

As understood from the above, the workpiece supply/conveyance device 2of the present invention can readily perform the workpiece deliveryoperation by the rotation of the arm body 26, which enables thecurtailment of a time from the end to the start of the machining of theworkpiece (a cycle time) of the machine tool 1 by the workpiece deliveryoperation.

SECOND EMBODIMENT

FIGS. 7( a) and 7(b) are concerned with a second embodiment of thepresent invention, where (a) is a front view of a main part of a machinetool including a workpiece supply/conveyance device and (b) is a planview of the same.

A workpiece supply/conveyance device of this embodiment includes twoloading devices (a first loading device 30 and a second loading device31) which supply different types of unmachined workpieces.

In this embodiment, the first loading device 30 is arranged at the sameposition as the loading device 27 of the foregoing embodiment, and thesecond loading device 31 is arranged at the same position as theunloading position 28 of the foregoing embodiment so as to face anunmachined workpiece holding section 29 of an arm 24. In the followingdescription, a first unmachined workpiece loading position IIIa is aposition which is on the downstream side in a rotating direction as seenfrom a spindle 13 and at which an unmachined workpiece is delivered tothe unmachined workpiece holding section 29 of the arm 24 from the firstloading device 30. Furthermore, a second unmachined workpiece loadingposition IIIb is a position which is on the upstream side of theposition IIIa and at which an unmachined workpiece is delivered to theunmachined workpiece holding section 29 of the arm 24 from the secondloading device 31.

In this embodiment, when three arms 24 in the four arms 24 are placed ata standby position IV, the first unmachined workpiece loading positionIIIa and the second unmachined workpiece loading position IIIb, theunloading device 28 is arranged at a position where it can receive amachined workpiece from a machined workpiece holding section 21 of theone remaining arm 24 and unload the same.

Therefore, also in this embodiment, while one arm 24 holds an unmachinedworkpiece which is to be next machined and is standby at the standbyposition IV, it is possible to simultaneously carry out the supply ofthe unmachined workpiece from one of the first unmachined workpieceloading position IIIa and the second unmachined workpiece loadingposition IIIb to the arm 24 and the conveyance of a machined workpiecefrom the arm 24 to the unloading device 28.

As the first loading device 30 and the second loading device 31, variouskinds of devices can be used. Since the first loading device 30 and thesecond loading device 31 of this embodiment are arranged on left andright sides of an axial line C2 as a boundary, they have the same basicconstitution except that they are symmetrical. As shown in FIG. 7, thefirst loading device 30 and the second loading device 31 have partfeeders 301 and 311 including hoppers 300 and 310 which store aplurality of unmachined workpieces, and linear feeders 302 and 312including linear guides 303 and 313 which linearly align the unmachinedworkpieces supplied from the part feeders 301 and 311 and guides each ofthe unmachined workpieces to a position near the unmachined workpieceholding section 29 of the arm 24 placed at the first unmachinedworkpiece loading position IIIa or the second unmachined workpieceloading position IIIb. The unmachined workpiece supplied to the tip ofthe linear feeder 302 or 312 is delivered to the unmachined workpieceholding section 29 of the arm 24 placed at the first unmachinedworkpiece loading position IIIa or the second unmachined workpieceloading position IIIb by, e.g., a push rod or robot hand not shown, orair pressure feed.

FIGS. 8( a) and 8(b) are enlarged cross-sectional views showing thespindle tip portion of a machine tool in this embodiment.

A grasping claw of a chuck 231 provided at the tip of the spindle 13 isformed into a stepped shape including a large diameter portion 231 a anda small diameter portion 231 b, and two types of workpieces W1 and W2having different diameters can be grasped. That is, as shown in FIG. 8(a), the small diameter workpiece W1 can be grasped at the small diameterportion 231 b, and as shown in FIG. 8( b), the large diameter workpieceW2 can be grasped at the large diameter portion 231 a.

According to such a constitution, the first loading device 30 and thesecond loading device 31 separately supply the workpieces W1 and W2, andeven if the workpiece to be machined is exchanged with a different typeof workpiece, the chuck 231 does not have to be replaced.

In this case, as a holder and a stopper which are provided in theunmachined workpiece holding section 29 and the machined workpieceholding section 21, a holder 293 and a stopper 294 for the smalldiameter workpiece W1 are prepared, and a holder 295 and a stopper 296for the large diameter workpiece W2 are prepared. In accordance with thechangeover of the workpieces W1 and W2, the holder 293, the stopper 294,the holder 295 and the stopper 296 are replaced.

Next, a function of the workpiece supply/conveyance device of thisembodiment will be described.

In the following, there will be described an example where an unmachinedworkpiece supplied from the first loading device 30 is first machinedand then an unmachined workpiece supplied from the second loading device31 is machined.

In a case where the unmachined workpiece supplied from the first loadingdevice 30 is machined, the driving of the second loading device 31 isstopped. A procedure of supplying the unmachined workpiece to the arm 24from the first loading device 30, delivering and receiving theunmachined workpiece and the machined workpiece with respect to thespindle 13, and delivering the machined workpiece to the unloadingdevice 28 and unloading is the same as in the foregoing embodimentexcept that a position of the unloading device 28 (the machinedworkpiece unloading device II) is different.

When a workpiece switching command is output from an NC device of themachine tool 1 (see FIG. 1), the driving of the first loading device 30is stopped, and the second loading device 31 is driven. When one arm 24is at the standby position VI, the unmachined workpiece holding section29 of the arm 24 placed at the second unmachined workpiece loadingposition IIIb is vacant, and hence the unmachined workpiece which is tobe machined after the switching is supplied to this unmachined workpieceholding section 29 from the second loading device 31.

It is to be noted that, at this time, the arms 24 placed at the firstunmachined workpiece loading position IIIa and the standby position IVhold unmachined workpieces before the switching, and hence, when thenumber of the remaining workpieces which are currently being machined istwo, the switching command from the NC device is preferably output.

The workpiece supply/conveyance device of this embodiment is alsouseful, for example, in a case where the unmachined workpiece isperformed to primary machining to form a semifinished product and thenthe semifinished product is further performed to secondary machining toprovide a finished product.

THIRD EMBODIMENT

The arrangement of the first loading device, the second loading deviceand the unloading device is not restricted to the above constitution.FIG. 9 is concerned with a third embodiment of the present inventionwhich is a modification of the second embodiment. In the thirdembodiment, the arrangement of the first loading device, the secondloading device and the unloading device in the second embodiment ischanged.

In this embodiment, a second loading device 33 is arranged at the sameposition as the loading device 27 in the first embodiment, and aunloading device 28 is arranged at the same position as the unloadingdevice 28 in the first embodiment. It is to be noted that the unloadingdevice 28 may be provided at the same position as the unloading device28 in the second embodiment. Further, a first loading device 32 isprovided so as to face an unmachined workpiece holding section 29 of anarm 24 placed at a standby position IV.

Also in this embodiment, a first unmachined workpiece loading positionIIIa is a position which is on the downstream side in a rotatingdirection as seen from a spindle 13 and at which an unmachined workpieceis delivered to the unmachined workpiece holding section 29 of the arm24 from the first loading device 32. Furthermore, a second unmachinedworkpiece loading position IIIb is a position which is on the upstreamside of the position IIIa and at which an unmachined workpiece isdelivered to the unmachined workpiece holding section 29 of the arm 24from the second loading device 31. The first unmachined workpieceloading position IIIa is also the standby position IV.

The workpiece supply/conveyance device of this embodiment functions inthe same manner as the workpiece supply/conveyance device of the secondembodiment. It is to be noted that, in this embodiment, the arm 24placed at the standby position IV (the first unmachined workpieceloading position IIIa) holds an unmachined workpiece before switching,and hence, when the number of the remaining workpiece which is currentlybeing machined is one, the switching command from the NC device ispreferably output.

FOURTH EMBODIMENT

FIG. 10 is concerned with a fourth embodiment of the present inventionwhich is another modification of the workpiece supply/conveyance deviceof the second embodiment.

In this embodiment, a first loading device 34 is provided to face anunmachined workpiece holding section 29 of an arm 24 placed at a firstunmachined workpiece loading device IIIa, and a first unloading device28 a is provided to face a machined workpiece holding section 21 of thearm 24 placed at the first unmachined workpiece loading position IIIa.In this embodiment, the first unmachined workpiece loading position IIIais also a first machined workpiece unloading position IIa.

Furthermore, a second loading device 35 is provided to face theunmachined workpiece holding section 29 of the arm 24 placed at a secondunmachined workpiece loading position IIIb, and a second unloadingdevice 28 b is provided to face the machined workpiece holding section21 of the arm 24 placed at the second unmachined workpiece loadingposition IIIb. In this embodiment, the second unmachined workpieceloading position IIIb is also a second machined workpiece unloadingposition IIb.

Moreover, the 4 arms provided to an arm body 26 is divided into twopairs of arms (arms 24 a and 24 b and arms 24 b and 24 b) placed on thesame axial lines so that one pair of arms 24 a and 24 a receive anunmachined workpiece from the first loading device 34 and the other pairof arms 24 b and 24 b receive an unmachined workpiece from the secondloading device 35.

In this embodiment, a first unmachined workpiece loading position IIIais a position which is on the downstream side in a rotating direction asseen from a spindle 13 and at which an unmachined workpiece is deliveredto the unmachined workpiece holding section 29 of the arm 24 a from thefirst loading device 34. Further, a second unmachined workpiece loadingposition IIIb is a position which is on the upstream side of theposition IIIa and at which an unmachined workpiece is delivered to theunmachined workpiece holding section 29 of the arm 24 b from the secondloading device 35. Additionally, the first unmachined workpiece loadingposition IIIa in this embodiment is also the first machined workpieceunloading position IIa at which the first unloading device 28 a receivesa machined workpiece from the machined workpiece holding section 21 andunloads the same, and the second unmachined workpiece loading positionIIIb is also the second machined workpiece unloading position IIb atwhich the second unloading device 28 b receives a machined workpiecefrom the machined workpiece holding section 21 of the arm 24 b andunloads the same.

Further, a second standby position IVb for the arm 24 b holding anunmachined workpiece is provided at the same position as the standbyposition IV according to each of the first to third embodiments, and afirst standby position IVa is provided at a position where the arm 24 ais stopped when the three arms 24 a, 24 b, and 24 b are placed at thefirst unmachined workpiece loading position IIIa, the second unmachinedworkpiece loading position IIIb, and the second standby position IV.

In this embodiment, the arm body 26 can rotate in a clockwise directionand a counterclockwise direction.

The workpiece supply/loading device of this embodiment functions asfollows.

An unmachined workpiece is supplied to each of the arms 24 a and 24 afrom the first loading device 34. Furthermore, an unmachined workpieceis supplied to each of the arms 24 b and 24 b from the second loadingdevice 35.

While a workpiece is being machined by the spindle 13, the arms 24 a and24 b holding unmachined workpieces are standby at the standby positionsIVa and IVb, respectively.

For example, when a workpiece which is to be machined this time is anunmachined workpiece held by the arm 24 b, the arm body 26 is rotated inthe counterclockwise direction to move the arm 24 b in a standby stateat the second standby position IVb to a workpiece delivery/receptionposition I facing the spindle 13. A workpiece delivering/receivingoperation of the spindle 13 and the arm 24 b at the workdelivery/reception position I is as described above.

Then, the arm body 26 is rotated in the counterclockwise direction tocause the arm 24 b holding a machined workpiece to pass the firststandby position Iva from the workpiece delivery/reception position Iand to move to the second unloading position IIb. Moreover, when aworkpiece is being machined by using the spindle 13, an operation ofdelivering the machined workpiece to the second unloading device 28 bfrom the machined workpiece holding section 21 of the arm 24 b and anoperation of supplying the unmachined workpiece from the second loadingdevice 35 to the unmachined workpiece holding section 29 are carriedout.

Thereafter, the arm 24 b is sequentially rotated to the second standbyposition IVb, the delivery/reception position I, and the secondunmachined workpiece loading position IIIb in the counterclockwisedirection to repeat the loading and the machining of unmachinedworkpieces and the unloading of machined workpieces.

When a workpiece which is to be next machined is an unmachined workpieceheld by the arm 24 a, the arm body 26 is first rotated in thecounterclockwise direction so that the arm 24 b which is standby at thesecond standby position IVb is placed at the workpiecedelivery/reception position I, and a machined workpiece is received bythe machined workpiece holding section 29 from the spindle 13. Then, thearm body 26 is rotated in the clockwise direction to move the arm 24 ain a standby state at the first standby position Iva to the workpiecedelivery/reception position I facing the spindle 13, and an unmachinedworkpiece is delivered to the spindle 13. Then, the arm body 26 isrotated in the clockwise direction to cause the arm 24 a holding amachined workpiece to pass the second standby position IVb from theworkpiece delivery/reception position I and to move the same to thefirst unloading position IIa. Further, when the workpiece is beingmachined by using the spindle 13, an operation of delivering themachined workpiece to the first unloading device 28 a from the machinedworkpiece holding section 21 of the arm 24 a and an operation ofsupplying the unmachined workpiece from the first loading device 34 tothe unmachined workpiece holding section 29 are carried out.

Thereafter, the arm 24 a is sequentially rotated to the first standbyposition Iva, the delivery/reception position I, and the secondunmachined workpiece loading position IIIa in the clockwise direction torepeat the loading and the machining of unmachined workpieces and theunloading of machined workpieces.

As explained above, in the workpiece supply/conveyance device of thisembodiment, while different types of workpieces are held by the arms 24a and 24 b and are standby at the first standby position Iva and thesecond standby position IVb and when a switching command is issued, thearm 24 a or the arm 24 b which are standby at the first standby positionIva or the second standby position IVb can be immediately moved to theworkpiece delivery/reception position, and the workpiece can be suppliedto the spindle 13, machined, and then unloaded.

In the workpiece supply/conveyance device of this embodiment, like thesecond and third embodiments, a predetermined number of one type ofworkpieces in different types of workpieces can be continuously machinedand then a predetermined number of the other type of workpieces can becontinuously machined, or different types of workpieces can bealternately machined.

FIFTH EMBODIMENT

FIG. 11 is concerned with a fifth embodiment of the present invention,and it is a front view for explaining a constitution of an arm body.

It is to be noted that like reference numerals denote members or partsequal to these in the foregoing embodiment in the following description,thereby omitting a detailed explanation thereof.

In this embodiment, 3 arms 240 are provided to an arm body 260 at equalintervals (intervals of 120°). At the tip of the arm 240, an unmachinedworkpiece holding section 29 and a machined workpiece holding section 21are provided on the same circumference A like the arm 24 in theforegoing embodiments.

In FIG. 11, when one arm 240 is standby at a standby position IV, one ofthe other two arms 240 and 240 is placed at a machined workpieceunloading position II, and a remaining arm is placed at a unmachinedworkpiece loading position III. An unmachined workpiece WB is suppliedfrom a loading device 27 to the unmachined workpiece holding section 29at the unmachined workpiece loading position III, and a machinedworkpiece is delivered from the machined workpiece holding section 21 toan unloading device 28 at the machined workpiece unloading position IIto be unloaded. The unmachined workpiece WB supplied from a loadingdevice 27 is held by the unmachined workpiece holding section 29 of thearm 240 placed at the standby position IV.

Upon terminating the machining of a workpiece at a spindle 13, the armbody 260 rotates in the counterclockwise direction by the same procedureas described above to move the arm 240 placed at the standby position IVto a workpiece delivery/reception position I (a moved state is indicatedby a virtual line). At this time, the machined workpiece and theunmachined workpiece. WB are delivered/received between the arm 240 andthe spindle 13 in the same manner as in the preceding embodiments. Whenthis delivery/reception is terminated, the arm body 260 rotates in thecounterclockwise direction to move the arm 240 holding the machinedworkpiece to the machined workpiece unloading position II. At this time,the other two arms 240 are placed at the unmachined workpiece loadingposition III and the standby position IV.

SIXTH EMBODIMENT

FIG. 12 is concerned with a sixth embodiment of the present invention,and it is a front view for explaining a constitution of an arm body.

It is to be noted that like reference numerals denote members or partsequal to those of the foregoing embodiments in the followingdescription, thereby omitting a detailed explanation thereof.

In this embodiment, two arms 340 are provided to an arm body 360 atequal intervals (intervals of 180°). At the tip of the arm 340, like thearms 24 and 240 in the foregoing embodiments, an unmachined workpieceholding section 29 and a machined workpiece holding section 21 areprovided on a circumference A.

In FIG. 12, when one arm 340 is standby at a standby position IV, theother arm 340 is placed at a workpiece supply position III. Further, anunmachined workpiece WB is supplied to the unmachined workpiece holdingsection 29 from a loading device 27.

The unmachined workpiece holding section 29 of the arm 340 placed at thestandby position IV holds the unmachined workpiece WB supplied from theloading device 27.

Upon termination of the machining of a workpiece by using a spindle 13,when the arm body 360 rotates in the counterclockwise direction to moveone arm 340 placed at the standby position IV to a workpiecedelivery/reception position I (a moved state is indicated by a virtualline), the delivery/reception of the machined workpiece and theunmachined workpiece WB is carried out between the arm 340 and thespindle 13.

When the delivery/reception of the machined workpiece and the unmachinedworkpiece WB is terminated between the spindle 13 and the arm 340, thearm body 360 rotates to move the arm 340 holding a machined workpiece WAat the workpiece holding section 21 to a machined workpiece unloadingposition II (a moved state is indicated by a virtual line). Furthermore,when the unmachined workpiece WB is being machined by using the spindle13, the machined workpiece WA is delivered from the machined workpieceholding section 21 to the unloading device 28 to be unloaded.Thereafter, the arm body 360 rotates to place the other arm 340 holdingthe unmachined workpiece WB to be machined at a standby position IV. Atthis time, one arm 340 is placed at a workpiece supply position III tosupply the unmachined workpiece WB from the unloading device 27.

In this embodiment, although not shown in particular, the unloadingdevice 28 may be arranged so that when the one arm 340 is standby at thestandby position IV, the other arm 340 is placed at the machinedworkpiece unloading position II. In this case, when the one arm 340 isstandby at the position IV, the other arm 340 delivers the machinedworkpiece WA to the unloading device 28. Moreover, when thedelivery/reception of the workpieces WA and WB is terminated between thespindle 13 and the one arm 340, the arm body 360 rotates to place theother arm 340 at the unmachined workpiece loading position III. At thistime, the machining of the unmachined workpiece WB is started at thespindle 13.

When the machining of the unmachined workpiece WB is being carried outby using the spindle 13, the unmachined workpiece WB is delivered fromthe loading device 27 to the other arm 340. Then, the arm body 360rotates to place the other arm 340 holding the unmachined workpiece WBat the standby position IV and also place the one arm 340 holding themachined workpiece WA at the machined workpiece unloading position II.

Furthermore, as shown in FIG. 13, tools T to cut a workpiece W can bedisposed to the arms 24, 24 a, 24 b, 240 and 340 in each foregoingembodiment, respectively. Although the tools T can be disposed to one ofthe upstream side and the downstream side in a rotating direction of thearm 24, 24 a, 24 b, 240, or 340, they may be disposed to both the sidesas shown in the drawing. Additionally, placing blade edges of the toolsT on the circumference A is sufficient.

When such a constitution is adopted to oscillate the arm 24, 24 a, 24 b,240, or 340 with respect to the workpiece W, the machining of theworkpiece W can be performed by using the tools T disposed to the arm24, 24 a, 24 b, 240, or 340. It is to be noted that the arm 24, 24 a, 24b, 240, or 340 utilized for the machining may be in a standby mode inwhich it holds the unmachined workpiece WB, or each arm may hold themachined workpiece WA received from the spindle 13.

Although the suitable embodiments of the present invention have beendescribed, the present invention is not restricted to the foregoingembodiments.

For example, the description has been given as to the structure wherethe arm body has the 2 to 4 arms arranged at equal intervals in theabove description, but the number of arms may be 5 or above.

Further, although the description has been given as to the structurewhere each of the unmachined workpiece holding section 29 and themachined workpiece holding section 21 inserts a workpiece into thecylindrical holder 291, a structure where the unmachined workpieceholding section 29 and the machined workpiece holding section 21 canhold an unmachined workpiece and a machined workpiece is sufficient, andvarious kinds of structures based on, e.g., air suction or magneticattachment can be adopted.

Furthermore, although the description has been given as to theconstitution where the machining is performed while switching differenttypes of workpieces in the second to fourth embodiments, a constitutionwhere the same type of workpieces are supplied from the plurality ofloading devices can be adopted so that a workpiece can be immediatelysupplied from one of the other loading devices even if a trouble such aslack of a workpiece in one loading device or clogging of a workpieceoccurs, thereby enabling a continuous operation for a long time.

INDUSTRIAL APPLICABILITY

The workpiece supply/conveyance device according to the presentinvention can be applied to not only a machine tool but all workpiecemachining apparatus which perform a predetermined operation to aworkpiece, e.g., an assembling machine or an inspection device.

1. A workpiece supply/conveyance device which includes a plurality ofarms radially extending from a rotation center, integrally rotates theplurality of arms around a rotation center, and places a workpieceholding section of one arm in the plurality of arms at a workpiecedelivery/reception position to deliver/receive the workpiece between aworkpiece machining apparatus and the workpiece holding section, whereinthe workpiece holding section includes an unmachined workpiece holdingsection that holds an unmachined workpiece and a machined workpieceholding section that holds a machined workpiece, and the plurality ofthe arms are integrally rotated in one direction to move each of thearms to an unmachined workpiece loading position at which the unmachinedworkpiece is received by the unmachined workpiece holding section, astandby position which is in a standby mode while holding the unmachinedworkpiece to be next machined in the unmachined workpiece holdingsection, a workpiece delivery/reception position at which the workpieceis delivered and received among the workpiece machining apparatus, theunmachined workpiece holding section and the machined workpiece holdingsection, and a machined workpiece unloading position at which themachined workpiece held in the machined workpiece holding section isunloaded.
 2. The workpiece supply/conveyance device according to claim1, wherein the unmachined workpiece holding section and the machinedworkpiece holding section of the workpiece holding section are arrangedin close proximity to each other on a common circumference having therotation center as the center, and the arm is rotated in one directionwhen placed at the workpiece delivery/reception position, whereby thearm is moved between a machined workpiece reception position at whichthe machined workpiece holding section receives the machined workpiecefrom the workpiece machining apparatus and an unmachined workpiecedelivery position at which the unmachined workpiece holding sectiondelivers the unmachined workpiece to the workpiece machining apparatus.3. The workpiece supply/conveyance device according to claim 1, whereinwhen one of the plurality of arms is at the standby position, one of theplurality of other arms is at the unmachined workpiece loading position,the workpiece supply/conveyance device being provided with a loadingdevice which supplies the unmachined workpiece to the arm placed at theunmachined workpiece loading position.
 4. The workpiecesupply/conveyance device according to claim 1, wherein when one of theplurality of arms is at the standby position, one of the plurality ofother arms is at the machined workpiece unloading position, theworkpiece supply/conveyance device being provided with an unloadingdevice which receives the machined workpiece from the arm placed at themachined workpiece unloading position and unloads the same.
 5. Theworkpiece supply/conveyance device according to claim 1, wherein theplurality of loading devices are provided in a path along which the armmoves from the machined workpiece unloading position to the standbyposition.
 6. The workpiece supply/conveyance device according to claim1, wherein a position of the arm is shifted in the order of theunmachined workpiece loading position, the standby position, theworkpiece delivery/reception position, and the machined workpieceunloading position.
 7. A machine tool including: a spindle which holds aworkpiece; a tool rest having a tool to machines the workpiece held bythe spindle; and a workpiece supply/conveyance device which delivers andreceives the workpiece to and from the spindle, wherein the workpiecesupply/conveyance device comprises a plurality of arms radiallyextending from a rotation center, and an unmachined workpiece holdingportion to hold an unmachined workpiece and a machined workpiece holdingsection to hold a machined workpiece which are provided to each of thearms, and the plurality of the arms are integrally rotated in onedirection to move each of the arms to an unmachined workpiece loadingposition at which the unmachined workpiece is received by the unmachinedworkpiece holding section, a standby position which is in a standby modewhile holding the unmachined workpiece to be next machined in theunmachined workpiece holding section, a workpiece delivery/receptionposition at which the workpiece is delivered and received among theworkpiece machining apparatus, the unmachined workpiece holding sectionand the machined workpiece holding section, and a machined workpieceunloading position at which the machined workpiece held in the machinedworkpiece holding section is unloaded.
 8. The machine tool according toclaim 7, wherein the unmachined workpiece holding section and themachined workpiece holding section of the workpiece holding section arearranged in close proximity to each other on a common circumferencehaving the rotation center as the center, and the arm is rotated in onedirection when placed at the work delivery/reception position, wherebythe arm is moved between a machined workpiece reception position atwhich the machined workpiece holding section receives the machinedworkpiece from the workpiece machining apparatus and an unmachinedworkpiece delivery position at which the unmachined workpiece holdingsection delivers the unmachined workpiece to the workpiece machiningapparatus.
 9. The machine tool according to claim 7, wherein when one ofthe plurality of arms is at the standby position, the workpiece graspedby the spindle is machined.
 10. The machine tool according to claim 7,wherein when one of the plurality of arms is at the standby position,one of the plurality of other arms is at the unmachined workpieceloading position, the machine tool being provided with a loading devicewhich supplies the unmachined workpiece to the arm placed at theunmachined workpiece loading position.
 11. The machine tool according toclaim 7, wherein when one of the plurality of arms is at the standbyposition, one of the plurality of other arms is at a machined workpieceunloading position, the machine tool being provided with an unloadingdevice which receives the machined workpiece from the arm placed at themachined workpiece unloading position and unloads the same.
 12. Themachine tool according to claim 6, wherein the plurality of loadingdevices are provided in a path along which the arm moves from themachined workpiece unloading position to the standby position.
 13. Themachine tool according to claim 12, wherein while different types ofworkpieces supplied from the plurality of loading devices are exchanged,the workpieces are machined.
 14. The machine tool according to claim 7,wherein a position of the arm is shifted in the order of the unmachinedworkpiece loading position, the standby position, the workpiecedelivery/reception position, and the machined workpiece unloadingposition.
 15. The machine tool according to claim 7, wherein a tool isattached to the arm, and the workpiece is machined by the tool with theaid of an swing operation of the arm.